Introduction to Ball Valves: General & Technical Details

1. General Introduction to Ball Valves

As a species of plug valve, the ball valve is a quarter turn, straight-through flow valve with a spherical ball-shaped closure member. Ball valves are widely used in gas, compressed air, liquid and non-abrasive slurry services as well as vacuum and cryogenic services. Because of the wiping rotary motion of the closure member, ball valves are ideal for non-abrasive slurry services or processes with particulates, since the ball port has a tendency to separate or shear the particulates upon closing movement.

According to the operation methods, ball valves can be categorized as manual ball valves and actuated ball valves. Manual ball valves can be either lever operated or worm gear operated that are best suited for stopping and starting flow (on-off service) and moderate throttling. Manual ball valves are typically found in sizes up to 12” (DN300) and in low pressure ratings Class 150 (PN20) through Class 600(PN100). Actuated ball valves can be further classified as pneumatic, electrical and hydraulic operation types based on its actuator’s driving method.

2. Design Standards and Applicable Range of Ball Valves

STANDARD	NAME	APPLICABLE RANGE
STANDARD	NAME	SIZE	PRESSURE RATING	APPLICATION
ISO 7121	Steel ball valves for general purpose industrial applications	DN15 ~ DN400	1.0 ~ 10 MPa	General
MSS SP 72	Ball Valves with Flanged or Butt-Welding Ends for General Service	DN15 ~ DN900	Class 150 ~ Class 900	General
API 6D	Specification for Pipeline Valves	DN50 ~ DN900	Class 150 ~ Class 2500	Oil & Gas Pipeline
JPI 7S 48	Steel Flange Ball Valves	DN15 ~ DN350	Class 150 ~ Class 300	Oil & Gas Pipeline
BS 5351	Steel Ball Valves for the Petroleum, Petrochemical and Allied Industries	DN8 ~ DN400	Class 150 ~ Class 800	Petroleum & Petro Chemical
BS 5159	Cast Iron and Carbon Steel Ball Valves for General Purposes	DN10 ~ DN600	1.0 ~ 10 MPa	General
ASME B16.34	Valves - Flanged, Threaded, and Welding End	DN3 ~ DN1300	Class 150 ~ Class 4500	General
API 608	Metal Ball Valves - Flanged, Threaded and Welding Ends	DN15 ~ DN600	Class 150 ~ Class 600	General
MSS SP 110	Ball Valves Threaded, Socket- Welding, Solder Joint, Grooved and Flared Ends	1/4" ~ 4"	1000 psig ~ 2000 psig	General
AWWA C507	Ball Valves, 6 in Through 48 in (150 mm Through 1200 mm)	6" ~ 48"	Class 150 ~ Class 300	Water Supply

3. Advantages VS. Disadvantages of Using Ball Valves

1) Advantages: ball valves can provide perfect sealing achieving bubble tight or “zero-leakage”. The opening & closing stroke can be completed in a very short time hence provides a quick response in On-Off service. The ball vales are not only lighter in weight and smaller in size than a peer gate or globe valve but also require smaller torque to operate. Ball valves have excellent performances in severe services such as high temperature, high pressure, cryogenic service, harsh acid & alkali corrosion and sea water environment.

2) Disadvantages: ball valves are not suitable for sustained throttling service. If the valve is partially open for an extended period under conditions of a high pressure drop across the ball, the soft seat(usually PTFE) may tend to flow around the edge of the ball orifice and possibly lock the ball in that position. And also in slurry applications, the suspended particles may settle and become trapped in valve body cavities causing wear, leakage or valve failure.

Related Articles: Introduction to Ball Valves: Design Features

Introduction to Ball Valves: Materials

Introduction to Ball Valves: Construction

Views: Author：hbmetals Date:15/04/02